Topological robustness of thermally disordered lattices: From average structures to ensemble electronic properties
Abstract
Band topology is usually assigned to a single crystal structure, yet at finite temperature a crystal is an ensemble of thermally disordered configurations with a fluctuating band gap. We ask whether the thermally averaged structure is a faithful proxy for this ensemble, taking Bi2Se3 as a representative topological insulator and classifying band ordering in each ab initio molecular dynamics snapshot by scaling the spin-orbit coupling. The averaged structure fails in two ways: it misses the Rashba-like spin splitting that instantaneous symmetry breaking produces in individual configurations, and it substantially underestimates the band-gap renormalization, whereas a small ensemble of harmonic Monte Carlo configurations reproduces both the mean and the spread of the gap. Using a band-inversion survival probability, we find that the band inversion of Bi2Se3 holds in every sampled configuration up to 600 K, above which individual configurations cross into normal band ordering well before the average gap closes. Topological robustness at finite temperature is thus a property of the distribution over configurations rather than of any single structure.
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BibTeX
@misc{rubel2026topological,
title = {{Topological robustness of thermally disordered lattices: From average structures to ensemble electronic properties}},
author = {Oleg Rubel and Karekin Sadikian},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.00963},
eprint = {2610.00963},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.00963},
}
RIS
TY - UNPB
TI - Topological robustness of thermally disordered lattices: From average structures to ensemble electronic properties
AU - Oleg Rubel
AU - Karekin Sadikian
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.00963
UR - https://arxiv.org/abs/2610.00963
AB - Band topology is usually assigned to a single crystal structure, yet at finite temperature a crystal is an ensemble of thermally disordered configurations with a fluctuating band gap. We ask whether the thermally averaged structure is a faithful proxy for this ensemble, taking Bi_2Se_3 as a representative topological insulator and classifying band ordering in each ab initio molecular dynamics snapshot by scaling the spin-orbit coupling. The averaged structure fails in two ways: it misses the Rashba-like spin splitting that instantaneous symmetry breaking produces in individual configurations, and it substantially underestimates the band-gap renormalization, whereas a small ensemble of harmonic Monte Carlo configurations reproduces both the mean and the spread of the gap. Using a band-inversion survival probability, we find that the band inversion of Bi_2Se_3 holds in every sampled configuration up to 600 K, above which individual configurations cross into normal band ordering well before the average gap closes. Topological robustness at finite temperature is thus a property of the distribution over configurations rather than of any single structure.
ER -